1. Field of the Invention
The present invention relates to a cooling system for an electronic device, and particularly, to a cooling system for an electronic device for efficiently cooling an electronic device which is required to perform a precise operation with a heat generation amount from itself being large, such as a computer and a server.
2. Description of the Related Art
In recent years, with improvement in the information processing technique and development of the Internet environments, the information processing amount which is required has increased, and data processing centers for processing various kinds of information in large volume are in the spotlights as business. For example, in the server room of the data processing center, a number of electronic devices such as computers and servers are installed in the concentrated state, and are continuously operated night and day. Generally, for installation of electronic devices in a server room, a rack mount method is a main stream. The rack mount method is the method for stacking racks (casings), which house electronic devices by dividing the electronic devices according to the functional unit, on a cabinet in layer. A number of such cabinets are arranged and disposed on the floor of a server room. These electronic devices which process information rapidly have improved in processing speed and processing capability, and the heat generation amount from the electronic devices continues to increase.
Meanwhile, these electronic devices require a constant temperature environment for operation, and the temperature environment for normal operation is set to be relatively low. Therefore, when the electronic devices are placed in a high-temperature state, they cause troubles such as system stops. Consequently, the fact is that the air-conditioning power which operates the air-conditioning machines for cooling the insides of the server rooms is significantly increased. Thus, reduction in the air-conditioning power becomes urgently necessary not only from the viewpoint of cost reduction in business management but also from the viewpoint of conservation of the global environment.
From such a background, the techniques for efficiently cooling electronic devices are proposed as seen in National Publication of International Patent Application No. 2006-507676, and Japanese Patent Application Laid-Open No. 2004-232927. National Publication of International Patent Application No. 2006-507676 proposes that a flow path for chilled air to flow in a closed loop via an electronic device is formed by mounting the electronic device with a back cover, a front cover and a side-mounted chilled air sub-frame, and providing a fan and a heat exchanger in the chilled air sub-frame.
Further, Japanese Patent Application Laid-Open No. 2004-232927 proposes that in an air-conditioning system for a computer room equipped with a rack group for storing electronic devices, which is internally mounted with an evaporator and a fan, the cooling air led from outside the room is caused to flow in an internal space under the floor to cool the electronic devices stored in the rack for storing electronic devices, through an evaporator, cools a condenser which is mounted on the rear surface of the rack for storing electronic devices, flows in a space at a rear surface or above the rack for storing electronic devices, and is discharged outdoor via a ventilator. Further, Japanese Patent Application Laid-Open No. 2007-127315 is not the invention relating to cooling of electronic devices, but introduces the art of naturally circulating a refrigerant between the evaporator and the condenser.